Use Promise.resolve in the events no queries are found

[nylin93]

When on the server doing:

getLoadableState(app).then(loadableState => { ... })
if no queries are found, throws an error because DeferredState is returned, not a Promise.

[codecov]

Codecov Report

Merging #6 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master       #6   +/-   ##
=======================================
  Coverage   92.66%   92.66%           
=======================================
  Files          12       12           
  Lines         109      109           
  Branches       27       27           
=======================================
  Hits          101      101           
  Misses          7        7           
  Partials        1        1

Impacted Files	Coverage Δ
src/server/index.js	87.27% <100%> (ø)	⬆️

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[gregberge]

Thanks, I added the test e67b5b2.